Three‐dimensional Porous Co Doped VN Nanosheet Arrays as Cathode Electrode for Alkaline Water Electrolysis

Abstract

AbstractAlkaline anion exchange membrane (AEM) water electrolysis is currently the most promising hydrogen production technology, and the development of non‐precious metal‐based hydrogen evolution reaction (HER) electrocatalysts with high performance and low price is one of the greatest challenges for large‐scale AEM. Although the reaction mechanism of HER under alkaline conditions is very different from acidic conditions, many researchers still believe that the HER activity is determined by Gibbs free energy for hydrogen absorption (ΔGH*) in all pH environments. In the meantime, vanadium‐based nitrides are rarely reported as alkaline HER catalysts due to the large density unoccupied orbitals of V cause high ΔGH* value. Herein, we prepare nanoporous VN sheet arrays (NSAs) with high specific surface by hydrothermal‐nitriding treatment, and then optimize its electronic structure via varying the doping amount of Co. As a result, the Co doped VN NSAs display an outstanding HER performance (overpotential of 37 mV at 10 mA cm−2 and Tafel slope of 41 mV dec−1), which is even close to the commercial Pt/C catalyst under alkaline conditions. Moreover, by combining theoretical calculations and HER performances under acid and basic conditions, we find that the adsorption/desorption of hydrogen on activity sites could not fully revealed by ΔGH*. This work opens up a new door to understand the mechanism of alkaline HER reaction and the development of HER electrocatalysts.